Problem: Solve for $k$, $- \dfrac{3k + 9}{3k + 7} = \dfrac{1}{7} $
Multiply both sides of the equation by $3k + 7$ $ -(3k + 9) = \dfrac{3k + 7}{7} $ Multiply both sides of the equation by $7$ $ -7(3k + 9) = 3k + 7 $ $-21k - 63 = 3k + 7$ $-63 = 24k + 7$ $-70 = 24k$ $24k = -70$ $k = -\dfrac{70}{24}$ Simplify. $k = -\dfrac{35}{12}$